It is well known in the art that dental fluoride is effective in impeding dental caries. Conventionally, dental fluoride is widely used in compositions in the form of rinses, toothpastes, and the like. Fluoride-containing mouth rinses that are formulated for daily use by consumers typically contain between 250 to 1,000 parts per million (ppm) fluoride, which ordinarily is present as sodium or stannous fluoride. Fluoride dentifrices typically contain 1,000 ppm to 5,000 ppm fluoride, which typically is present as sodium fluoride or sodium monofluorophosphate. Additionally, the prior art has provided self-applied fluoride gels, which typically have a fluoride content of up to 5,000 ppm. Office-administered topical fluoride gels, such as acidulated phosphate fluoride (APF) typically contain about 12,000 ppm (1.2%) fluoride.
The cariostatic effects of the various heretofore described fluoride regimens are believed to derive from their ability to deposit fluoride in plaque and salvia and onto the surfaces of teeth and other tissues in the mouth. Although the deposited fluoride is labile and leached out with time, daily applications of fluoride, such as via rinses and toothpastes, can maintain an elevated level of fluoride in the mouth. Additionally, the occasional application of gels, whether self-applied or office-administered, can further assist in maintaining an elevated content of fluoride on the surfaces of teeth.
Calcium fluoride, for CaF2, is recognized in the art as being a significant labile oral fluoride reservoir. Numerous efforts have been made to provide compositions that allow for introduction of calcium fluoride to oral cavities. For instance, in Chow, L. and Takagi, S., “Deposition of Fluoride on Tooth Surfaces by a Two-Solution Mouthrinse In Vitro,” Caries Res. 25:397-401 (1991), the inventors of the present application report that a rinse that contains both soluble calcium and fluoride did not increase fluoride deposition, because CaF2 formed by rapid precipitation from a highly supersaturated solution was unable to be retained in a model substrate in vitro. Calcium fluoride may be introduced in a sustained precipitation process where hexafluorosilicate is a source of fluoride. See Vogel, G. et al., “In Vivo Fluoride Concentrations Measured for Two Hours After a NaF or a New Two-Solution Rinse,” J. Dent. Res. 71:448-452 (1992). Similarly, enhanced fluoride deposition can be obtained from other systems; see, e.g., U.S. Pat. No. 5,476,647 (describing a complexed calcium source); U.S. Pat. No. 5,891,448 (describing a calcium fluoride inhibitor, such as citrate). In another approach, a calcium rinse is administered first, allowing calcium ions to penetrate into the surfaces of an oral substrate. Subsequently, fluoride is administered, causing CaF2 to form within the surfaces of the oral substrates. Vogel, G. et al., “Calcium Greatly Increases Salivary Fluoride from Fluoride Dentifrices/Rinses (abstract 3268),” J. Dent. Res. (Spec Iss. A) 84 (2005).
Some of the prior art formulations are not stable for storage and transport, and typically, these formulations require that two components be provided. The two components must be combined and then used immediately. Additionally, certain prior art formulations are limited in the amount of fluoride that can be administered. For instance, certain compositions appear to be functional only when the fluoride concentration is no higher than 250 ppm for rinses, and no higher than 1,000 ppm for dentifrices.
The invention seeks, in certain embodiments, to provide a single composition that is stable for storage and transport as against precipitation of a fluoride containing material but that allows a fluoride containing material to precipitate in a human oral cavity. In some embodiments, the invention seeks to provide compositions that allow for greater deposition of fluoride than that permitted in the heretofore described products.